Showing papers on "Growing season published in 1987"
TL;DR: Among species, differences in ozone uptake and response can be predicted from differences in the inherent leaf diffusive conductance, and for an equivalent dose within a single growing season, agricultural crops are the most sensitive to ozone.
Abstract: Published information about the effects of ozone on plants and ecosystems is synthesized into a conceptual model to explain the response of evergreen conifers, deciduous hardwoods and agricultural crops to ambient levels of ozone pollution. The effects of ozone on carbon balance and growth of individual plants can be quantified on the basis of concentration, external dose (concentration x duration of exposure), or uptake. For an equivalent dose within a single growing season, agricultural crops are the most sensitive to ozone, with hardwoods intermediate and conifers least sensitive. In contrast, all species display a similar decline in photosynthesis and growth in response to equivalent total uptake or uptake per leaf life span, with trees somewhat less sensitive than agricultural crops on a calendar time scale, but slightly more sensitive on a relative (leaf life span) time scale. Among species, differences in ozone uptake and response can be predicted from differences in the inherent leaf diffusive conductance.
610 citations
TL;DR: Spores of Gigaspora and Scutellospora species predominated in the root zones of three major plant species growing in the barrier dunes extending from northern New Jersey to Virginia, and Dominance by a single fungal species was inversely correlated with distance south and with temperature parameters.
Abstract: Spores of Gigaspora and Scutellospora species predominated in the root zones of three major plant species growing in the barrier dunes extending from northern New Jersey to Virginia. Similarity in edaphic factors, vegetation, daylength during the growing season, and precipitation along a 355 km transect permitted study of the composition of the VAM fungal community in response to temperature. Twenty-three species of VAM fungi were recovered. Dominant species along the transect were G. gigantea, Acaulospora scrobiculata, and S. dipapillosa. Some species were more abundant in the northern (cooler) regions of the transect and others were more abundant in the southern regions. Average VAM fungal species richness was positively correlated with distance south along the transect and with temperature parameters. Temperature effects on the VAM fungal community may be separated into two components, a direct effect on the fungi and an indirect effect mediated through the host plant. Plots of rank/log Importance Value depicted the structure of the VAM fungal community and were of use in identifying severe habitats where heat stress appeared to be the controlling factor. Dominance by a single fungal species was inversely correlated with distance south and with temperature parameters. It was most pronounced in northern sites and in the root zones of heat-stressed Ammophila breviligulata plants growing near the species' southern limit.
233 citations
TL;DR: The fall armyworm, Spodoptera frugiperda, has a high reproductive rate of 900–1000 eggs per female, a relatively short generation time of 30 days and good dispersal ability, which makes it a successful colonizing species.
Abstract: The fall armyworm, Spodoptera frugiperda (J. E. Smith), has a high reproductive rate of 900–1000 eggs per female, a relatively short generation time of 30 days and good dispersal ability. These traits make it a successful colonizing species. There is a large body of circumstantial evidence that migration is a major component in the life history strategy of this species. Although the fall armyworm is unable to survive the winter in the United States except in southern areas of Florida and Texas, it redistributes itself over most of the eastern United States each growing season. Long-range movement from Mississippi to Canada in 30 hr on a low-level jet stream was documented on one occasion with synoptic weather maps. Many fall armyworm moths have been collected in the Gulf of Mexico as far as 250 km from land, indicating the possibility of seasonal trans-Gulf migration between the United States and the tropics. Electrophoretic analyses of populations of a corn “race” of fall armyworm collected throughout the Caribbean Basin indicated low genetic heterogeneity. Nei’s genetic distance estimate (0.015) and Wright’s Fst value (0.032) both suggested undifferentiated populations with interbreeding across the entire geographic range. Wet and dry seasons in the east and west coast of Central America and elsewhere in the tropics alternate with each other so that only one habitat is available at a time. This fluctuation in available habitat is proposed as the templet that led to the evolution and maintenance of migration in the colonizing life history strategy of the fall armyworm.
196 citations
TL;DR: Spatial and temporal variation in these constituents produces plant parts, individuals and species with differential resistance to insect herbivores.
104 citations
TL;DR: Competition between ponderosa pine seedlings and various grasses and forbs was studied on :I site in northern Arizona burned in 1982 by a wildfire, indicating that competition occurred for both moisture and available nitrogen.
Abstract: Competition between ponderosa pine seedlings and various grasses and forbs was studied on :I site in northern Arizona burned in 1982 by a wildfire Two-yearold pine seedlings were planted in 305 x 305 m plots in April 1983, followed by the sowing of grass and forb seeds on the same plots in July 1983 after summer rains had begun Predawn xylem water potential of the pine seedlings was measured biweekly throughout the 1983 and 1984 growing seasons Extractable soil nitrogen was measured at the beginning and end of both growing seasons After the wildfire, nitrate and ammonium levels were significantly higher in the burned area than in an adjacent unburned area Nitrate and ammonium concentrations in various grass treatment plots were significantly (P < 005) different at both the beginning and end of the growing season Pine seedling xylem water potential differed among treatments, with potentials being lowest on plots sown with Agrtpyron deserrorrr/n The differences in seedling xylem water potential and available soil nitrogen were reflected in differences in pine seedling growth The most effective competitors were Agropym d~~scworwn and Lkwtylk g/o177~~1~71~ Results indicated that competition occurred for both moisture and available nitrogen FOR SCI 33(2):356-366 ADUITIONAI
84 citations
TL;DR: The responses shown by the studied species suggest that dehydration tolerance plays a role in plant distribution and that environmentally induced shifts in this tolerance are a significant phenomenon in natural plant communities.
Abstract: Electrolyte leakage from leaf discs (measured as an index of dehydration tolerance) increased as water potentials of excised leaves declined for field-grown saplings of six woody species. Until late in the growing season (mid-August), leaves of Cornus florida L. exhibited greater leakage than those of other species; however, in August and September leakage in this species was much reduced, indicating apparent hardening in response to mid-season drought. Leaves of Quercus alba L., Q. rubra L. and Q. velutina Lam. generally exhibited less electrolyte leakage than did those of Acer saccharum Marsh, and Juglans nigra L. over the season. Moreover, leaves of Quercus species showed a reduction in electrolyte leakage late in the season similar to (but less accentuated than) that of C. florida. Saplings of A. saccharum and J. nigra showed little and no drought-hardening response, respectively. The responses shown by the studied species suggest that dehydration tolerance plays a role in plant distribution and that environmentally induced shifts in this tolerance are a significant phenomenon in natural plant communities.
79 citations
TL;DR: In this paper, shoot elongation of treeline white spruce trees was studied on a transect through an area of forest succession during 1983 and 1984, relative to ground temperatures, air temperatures, and precipitation.
Abstract: Five crown forms of treeline white spruce are used to define open forest, forest-tundra, and tundra regions at Churchill, Manitoba, Canada. Shoot elongation of 25-, 50-, and 100-yrold open forest trees was studied on a transect through an area of forest succession during 1983. During 1984, shoot elongation of different crown forms was examined relative to ground temperatures, air temperatures, and precipitation. Stem and branch elongation of open forest trees was greatest and occurred over the longest period of time, followed by forest-tundra trees, and tundra trees. The increasing density of spruce in the zone of invading open forest is associated with moss development that moderates the ground temperature, increasing the lower root zone temperature early in the growing season and maintaining lower temperatures in the upper root zone later in the season. Continued moss accumulation coincides with permafrost formation into the root base. On the foresttundra and tundra, moss development is patchy. Early warming of the peat surface results in drying that impedes heat influx to the lower root zone. The temperatures in the lower root zone appear limiting to forest-tundra trees and restricting to tundra trees at the start of the growing season. Shoot elongation is over before the upper root zone becomes very hot. Treeline crown forms are grouped according to similar patterns of elongation and common types of development. The wind-abraded crown forms are caused by slow growth that leaves a tree exposed to wind effects for a longer period of time.
69 citations
TL;DR: Experiments with excised one-year-old extension canes indicated that the mobilization of macro and micronutrients stored in the plant from the previous season could have supported 20 to 40 % of the leaves on the vines during the first 30 d of growth.
Abstract: The accumulation of macro and micronutrients by leaves of 30 mature kiwifruit vines (Actinidia deliciosa var. deliciosa Hayward) from two high-producing orchards was recorded over a growing season. An assessment was also made of the extent of which mobilization of nutrients stored in the vine from the previous season contributed to the nutrient status of the leaves during the early part of the growing season. The seasonal patterns for the concentrations of the various nutrients in the leaves could be broadly grouped into three types. Concentrations of potassium declined throughout the season, whereas nitrogen, phosphorus, copper and zinc concentrations declined initially but reached values which remained relatively constant by mid-season. For calcium, magnesium, sulphur, boron, manganese and iron, concentrations in the leaves also declined initially but then increased for the remainder of the season. There was no apparent seasonal pattern for sodium or molybdenum. A strong association was found between soil temperature and the concentration of potassium in the leaf. The period of greatest accumulation of nitrogen, potassium, phosphorus, sulphur, copper and zinc by the leaves occurred from leaf emergence to fruit set. Magnesium, calcium, boron, iron and manganese differed from the other nutrients in that the rate of accumulation was relatively constant throughout the season. Experiments with excised one-year-old extension canes indicated that the mobilization of macro and micronutrients stored in the plant from the previous season could have supported 20 to 40 % of the leaves on the vines during the first 30 d of growth. The developing fruit had a marked effect on the potassium and nitrogen status of the leaves, particularly those close to fruit. The substantial losses of potassium (21 to 37 %) and nitrogen (16 to 22 %) from the leaves after fruit set were sufficient to satisfy the requirements of at least 40 % of the fruit on the vine. The much smaller losses of the other nutrients from the leaves (less than 15 % of the total quantity present) reflected their lower mobility in the plant and the small demand by the developing fruit for these elements.
62 citations
TL;DR: In an attempt to assess maximum biomass production of willows, field experiments with irrigation and fertilization (through the same system) were carried out in the south of Sweden (57°N) as mentioned in this paper.
54 citations
TL;DR: In this article, the amount of ferric hydroxide plaque deposited on Typha latifolia roots varied between wetlands submerged throughout the growing season and was positively correlated with extractable iron in the substrate and pH, and negatively correlated with the percent organic matter and percent inorganic carbonates in the soil.
Abstract: The amount of ferric hydroxide plaque deposited onTypha latifolia roots varied between wetlands submerged throughout the growing season. Plaque formation was positively correlated with extractable iron in the substrate and pH, and negatively correlated with the percent organic matter and percent inorganic carbonates in the soil. All the above correlations were significant but weak, and in a stepwise regression analysis these four soil factors accounted for 72% of the variation in plaque deposition. Plaque formation was unrelated to soil texture.
54 citations
TL;DR: The effects of plant chemistry and the nutritional needs of geese on food choices were modified by the need to select a safe feeding site.
Abstract: We investigated the influence of interspecific and seasonal variations in plant chemistry on food choices by adult and gosling Canada Geese, Branta canadensis, on Cape Cod, Massachusetts. The geese fed primarily on the abundant marsh grasses, Spartina spp., and rushes, Juncus gerardi, early in the growing season and switched to a greater dependence on eelgrass, Zostera marina, later. Forbs were generally avoided all season even when growing within patches of abundant species. The avoidance of forbs was related to their low abundance and their high concentrations of deterrent secondary metabolites. Differences in plant chemistry also determined the switch from marsh graminoids to Z. marina during the growing season. Marsh grasses were higher than Z. marina in nitrogen, particularly in the spring when the nitrogen requirement of geese is especially high. Z. marina was a better source of soluble carbohydrates and was the preferred food during the summer when the need to build up energy reserves may be more critical to geese than protein intake. Goslings, which require a diet higher in nitrogen than do adults, fed on marsh graminoids later into the growing season than the adults. The nitrogen content of the diets of goslings was significantly higher than that available to them in the plants, indicating that they selected for introgen. The diets of non-breeding adults in the spring and all geese in mid summer closely reflected the nutrient content of the plants. The diet of breeding adults was more similar to that of their goslings than to that of non-breeding adults. The effects of plant chemistry and the nutritional needs of geese on food choices were modified by the need to select a safe feeding site.
01 May 1987
TL;DR: In this article, the authors used kriging to estimate 7-h seasonal mean O3 concentrations for crop growing regions of the United States for each of the major crop growing areas for 1978-1982.
Abstract: Using kriging, a statistical technique, the National Crop Loss Assessment Network (NCLAN) program estimated growing season 5-month (May-September) ambient 7-h mean O3 concentrations for each of the major crop growing areas of the United States for 1978-1982. The O3 estimates were used to predict economic benefits anticipated by lowering O3 levels in the United States. This paper reviews NCLAN’s use of kriging to estimate 7-h seasonal mean O3 concentrations for crop growing regions. Although the original kriging program used by NCLAN incorrectly calculated the diagonal elements of the kriging equations, this omission did not result in significant errors in the predicted estimates. Most of the data used in estimating the 7-h seasonal values were obtained from urban areas; the use of these data tended to underestimate the 7-h seasonal O3 concentrations in rural areas. It is recommended that only O3 data that are representative of agricultural areas and have been collected under accepted quality assurance pro...
TL;DR: It was concluded that the timing of rainfall within a growing season was important in that it conferred an advantage to one or other of these species which differed markedly in their temporal ability to respond to favourable conditions of soil moisture with shoot growth.
Abstract: (1) Grass shoot yields in a semi-arid rangeland in south-western Zimbabwe were recorded over 5 years to observe patterns of growth in relation to the erratic rainfall characteristics of the region. (2) Total grass yield, and the growth of the three predominant species (Cymbopogon plurinodis (Stapf) Stapf ex Burtt Davy, Heteropogon contortus (L.) Roem. & Schult. and Themeda triandra Forssk.), were interpreted in relation to the availability of soil moisture in the growing season. Different growth strategies were inferred from patterns of shoot growth and of phenology. (3) It was concluded that the timing of rainfall within a growing season was important in that it conferred an advantage to one or other of these species which differed markedly in their temporal ability to respond to favourable conditions of soil moisture with shoot growth. (4) This phenomenon could account for observed differences in the proportions of these species from year to year and might have important implications for rangeland improvement. CR - Copyright &169; 1987 British Ecological Society
TL;DR: In this article, a procedure was developed from field studies in the San Joaquin Valley, California, U.S.A. that allows cotton (Gossypium hirsutum L.) ψ l's to be adjusted to common climatic evaporative demand conditions.
TL;DR: Grazing did not influence VAM colonization, although grazed plants which were growing in non-fumigated soil had significantly lower colonization levels than any other treatment, and mycorrhizal colonization had no effect upon plant, growth rates or size.
Abstract: Summary
Fumigated and non-fumigated plots were planted with several species of either mycorrhizal or non-mycorrhizal grasses. These plots were either inside or outside enclosures which allowed grazing by native North American ungulates and longhorn cattle. The morphology and growth of plants as well as the level of vesicular-arbuscular mycorrhizal (VAM) development were followed over one growing season during which growing season precipitation was 50 % of the normal level. Grazing was the most important treatment effect, greatly reducing plant size and relative growth rates. Mycorrhizal colonization had no effect upon plant, growth rates or size. Even in grazed plots where nutrient content and soil moisture were higher, no mycorrhizal effect on plant growth was observed. Grazing did not influence VAM colonization, although grazed plants which were growing in non-fumigated soil had significantly lower colonization levels than any other treatment.
TL;DR: Osmotic adjustment may be an acclimation response to short-term drought during the growing season, and may aid in survival during the long dry season by limiting dehydration of the growing points.
Abstract: Eustachys paspaloides was studied under conditions of water stress and simulated grazing (clipping) in the laboratory. Leaf and soil water potentials and leaf elongation rate (LER) were monitored during a 41-day drying period, and following rewatering. Water relations characteristics of tillers were derived from pressure-volume curves during the drought and recovery periods. Water stress developed more slowly in clipped than in unclipped plants; predawn water potentials declined at mean rates of 0.13 and 0.38 MPa day-1 in clipped and unclipped plants, respectively. Consequently, leaf elongation of clipped plants continued approximately a week longer during the drying period than when plants were not clipped. Following rewatering, LER increased from zero to steady levels over 4 days. Osmotic adjustment due to solute accumulation occurred in tillers of water-stressed plants. The difference in solute potential at full turgor between well-watered and stressed plants was 0.29 and 0.20 MPa for clipped and unclipped plants, respectively. The delay in permanent wilting afforded by lowered osmotic potential was about 1 day, indicating that osmotic adjustment is not a mechanism for reducing the effect of water stress on growth during long-term drought in Eustachys. However, osmotic adjustment may be an acclimation response to short-term drought during the growing season, and may aid in survival during the long dry season by limiting dehydration of the growing points.
TL;DR: In this article, the capacity of monocultural stands of crested wheatgrass, giant wildrye, streambank wheatgrass and Wyoming big sagebrush to deplete water from a clay-loam soil was compared.
Abstract: This study compared the capacity of monocultural stands of crested wheatgrass, giant wildrye, streambank wheatgrass, and Wyoming big sagebrush to deplete water from a clay‐loam soil. Soil water balance of a natural sagebrush steppe was used as a reference point. Transplanted crested wheatgrass plants extracted 243 mm of water from the soil during the first growing season, using most of the plant‐available water. The other species extracted less water, but evapotranspiration from all stands was well over the average annual precipitation for the study area (224 mm). In the second year, all four species extracted water from the entire 2.2‐m profile and used most of the available water. The native community removed essentially all of the available soil moisture in each of the three years. Despite phenological and morphological differences among species, patterns of water depletion were generally similar. Seasonal evapotranspiration varied little among species but was correlated with the soil water av...
TL;DR: In this article, water and temperature measurements were made at a clearcutting in Jadraas, central Sweden, to give appropriate information for nutrient flow calculations and soil biological research, and the physically based model, SOIL, was used to analyse these observations and to estimate the effects of clearcutting.
Abstract: Soil water and temperature measurements were made at a clearcutting in Jadraas, central Sweden, to give appropriate information for nutrient flow calculations and soil biological research. Compared to uncovered plots, slash‐covered plots were 1–2°C colder and had 3–6 volume percent higher water content in the 5 cm thick humus‐layer during the growing season following cutting. Relative to air, soil temperatures became warmer at both treatments during the second season and differences between uncovered and covered plots decreased. Tension dynamics in the mineral soil was most pronounced in uncovered plots, especially during the first dry growing season. The physically based model, SOIL, was used to analyse these observations and to estimate the effects of clearcutting. Simulated snow and frost depths, soil temperatures, water contents and tensions as well as ground water table were compared with measured data during a period of one to four years. Physical parameter values were estimated from independent mea...
TL;DR: Reducing early season vegetative growth with the PGRs proved to be advantageous to productivity under water stress and counterproductive under nonlimiting water conditions.
Abstract: Corn (Zea mays L.) grown under the semiarid conditions of the Central Great Plains requires supplemental irrigation to obtain maximum yields. This practice has become increasingly less profitable as the cost of application of irrigation water has risen. It may prove to be more cost effective to reduce the water requirement of corn by limiting the vegetative development of the plant. Two anti-gibberellin, seed-applied, experimental plant growth regulators (PGRs), BAS 106. .W and BAS 110. .W, were used on corn grown under low and high levels of irrigation in a 2-yr (1984 and 1985) field study on a Rago silt loam soil (fine, montmorillonitic, mesic Pachic Argiustolls) to determine the effect of these PGRs on vegetative growth, water use, water stress, grain yield, and yield components. The PGRs were applied at three rates in both years (0, 100, and 200 mg a.i. kg-' of BAS 106. .W in 1984 and 0, 125, and 250 mg a.i. kg-' of BAS 110. .W in 1985). Increasing application rates of the PGRs caused a significant reduction in early season plant height, leaf area index (monitored in 1985 only), and dry matter accumulation (monitored in 1985 only), resulting in reduced early season evapotranspiration in both years. The PGR treatments reduced plant water stress during silking and early grain fill, particularly under the low irrigation treatment. The changes in plant growth and development associated with the PGRs resulted in a 9 and 16% increase in grain yield in 1984 and 1985, respectively, under the low irrigation treatment and a 7 and 9% reduction in grain yield in 1984 and 1985, respectively, under the high irrigation treatment. Therefore, reducing early season vegetative growth with the PGRs proved to be advantageous to productivity under water stress and counterproductive under nonlimiting water conditions. Additional index words: Zea mays L., Yield components, Irrigation, Leaf area, Plant growth regulator._______ Y of many crops grown in the Central Great Plains are critically tied to water availability during the growing season and high evapotranspiration levels (Stewart et al, 1975; Hanks et al., 1978; Musick andDusek, 1980;Garrity et al, 1982;Stegman, 1982). But the amounts of water needed for maximum corn (Zea mays L.) grain yields in this area, where annual precipitation averages 420 mm, are not available. Reported values for seasonal evapotranspiration of corn vary widely (440 to 1000 mm), as influenced by available water and local environmental parameters (Shaw et al., 1958; Musick and Dusek, 1980; Eck, 1984). For maximum yields, the difference between water required and precipitation must come from irrigation. Increasing pumping costs and declining water tables in some areas make use of irrigation unprofitable. Perhaps a more cost effective method of corn production for maximum economic return in this area would be to reduce the water requirement of corn. One way of reducing water use may be to limit vegetative development of the plant. Water stress is an effective means for limiting vegetative development, but the time at which the stress occurs greatly influences yield reductions. Shaw (1977) reviewed research done regarding the timing of water stress and effects on grain yield. Generally, it is reported that corn is relatively tolerant to water stress in the vegetative stage, very sensitive to water stress during the period of tasseling, silking, and pollination, 1 Joint contribution from Dep. of Agronomy, Colorado State Univ., Colorado Agric. Exp. Stn., and U.S. Department of Agriculture, Agricultural Research Service. Work supported in part by a gift from the BASF Wyandotte Corp., Agricultural Chemicals Group, P.O. Box 181, Parsippany, NJ 07054. Received 14 Dec. 1985. 2 Assistant professor, Dep. of Agronomy, Colorado State Univ., Ft. Collins, CO 80523, and research agronomist, U.S. Department of Agriculture, Agricultural Research Service, Central Great Plains Res. Stn., Akron, CO 80720, respectively. Published in Agron. J. 79:103-109 (1987). 104 AGRONOMY JOURNAL, VOL. 79, JANUARY-FEBRUARY 1987 and moderately sensitive during the grain-filling stage. Water stress during the vegetative period stimulates deeper, more prolific root growth (Mayaki et al., 1976; Shaw, 1978) while reducing top growth, thereby increasing the root/shoot ratio (Sharp and Davies, 1979; Westgate and Boyer, 1985b). Such responses to water deficits would have the beneficial effect of reducing leaf area and presumably evapotranspiration while at the same time providing a greater amount of available soil water due to the increased rooting volume. The reduced evapotranspiration should conserve soil water early in the season so that more is available later during the more critical growth stages of reproduction and
TL;DR: Common scab and silver scurf were both decreased by irrigation but in two years, black dot was increased, and the relative importance of black dot could increase in irrigated crops where fungicides are used to control silver scirf.
Abstract: SUMMARY
In field experiments seed tubers affected with powdery scab cankers were planted and the effect on disease incidence of timing of irrigation and some seed-tuber fungicides was investigated over 3 yr. For 2 yr, irrigation to maintain soil wetter than—20 centibars (—20 kPa) during the first half of the growing season increased disease compared to unirrigated plots. Disease incidence was not affected by irrigation at 2 wk intervals or when applied during the second half of the season. Little disease developed in 1983 even in irrigated plots, probably because of high soil temperatures. None of the fungicides tested gave consistent disease control.
Common scab and silver scurf were both decreased by irrigation but in two years, black dot was increased. The relative importance of black dot could increase in irrigated crops where fungicides are used to control silver scurf.
TL;DR: Biomass production in fertilized trefoil plots in the fourth year exceeds that of local forests by 50%, and may be comparable to corn productivity in the area.
TL;DR: The composition of lignin (by nitrobenzene oxidation) varied with the plant, harvesting frequency, and maturity, although changes were often more pronounced early in the growing season.
TL;DR: The present and previous experiments suggest that the distribution of subalpine eucalypts is dependent upon the interaction of a range of factors including the severity of winter frosts, resistance to growing season frosts and the suitability of the site for frost hardening and the degree of waterlogging.
Abstract: Marked interspecific differences in frost resistance were shown to exist between eucalypt seedlings grown in reciprocal field transplant trials conducted at a frost hollow on Snug Plains, south-eastern Tasmania Populations of the six eucalypt species tested naturally inhabited the margins and base of this frost hollow A growing season frost of - 55°C caused substantial damage to E delegatensis, E pulchella, E urnigera, E johnstonii and E coccifera but only slight damage to E gunnii A winter frost of - 105°C caused markedly less damage than the growing season frost, suggesting that appreciable hardening occurs in winter and that growing season frosts may play a significant role in determining the distribution of subalpine eucalypts E pulchella appeared more resistant to growing season frosts than E delegatensis while the reverse occurred in all but one of the experimental gardens during winter frosts The reasons for this reversal and its significance are discussed Frost chamber experiments confirmed the major differences between species in frost resistance and the importance of hardening The reciprocal transplant trials suggested that seedlings from subgenus Symphyomyrtus were more frost resistant than those from subgenus Monocalyptus in sites prone to waterlogging This was sup- ported by frost chamber trials in which a significant interaction between frost resistance and waterlog- ging was demonstrated Species from subgenus Monocalyptus showed a reduced ability to harden under waterlogged conditions compared with species from subgenus Symphyomyrtus This interaction may be of ecological importance since species from subgenus Monocalyptus do not occur in cold, waterlogged sites at Snug Plains The present and previous experiments suggest that the distribution of subalpine eucalypts is dependent upon the interaction of a range of factors including the severity of winter frosts, resistance to growing season frosts, the suitability of the site for frost hardening and the degree of waterlogging
TL;DR: The authors examined the agricultural and hydrological perspectives of the 1986 Southern United States drought via a climatological time series and concluded that the 1986 drought was part of a change in recent years from the wet weather of the 1960s and much of the 1970s.
Abstract: The dry and hat weather in the southeast United States during the first seven months of 1986 caused record drought. The agricultural and hydrological perspectives of this drought are examined via a climatological time series. Late nineteenth and twentieth century climate data from the most severely affected areas indicate that from an agricultural perspective the beginning and middle of the 1986 growing season was by far the worst on record. On the other hand, from a hydrological perspective the drought was not of sufficient duration to stand out as such an extreme anomaly. The 1986 drought is part of a change in recent years from the wet weather of the 1960s and much of the 1970s. At this time, there is no evidence to suggest that this change is anything more than another in a series of climate fluctuations typical throughout the climate records of many areas.
TL;DR: In this paper, Salix alaxensis Anderss. (Cov.) is used to restore moose habitat on sites disturbed by construction of the Trans-Alaska Pipeline System on the North Slope of Alaska.
Abstract: Methods for planting Salix alaxensis Anderss. (Cov.) to restore moose habitat were tested on sites disturbed by construction of the Trans-Alaska Pipeline System on the North Slope of Alaska. Stands of S. alaxensis were successfully established by planting frozen, dormant cuttings or fresh cuttings as soon as the soil thawed. Cuttings with an apical diameter of 0.6 to 1.5 cm and a total length of 33 to 38 cm, planted to a minimum depth of 15 cm, had the highest survival and growth. Fertilization during the first or third growing season and polyethylene mulch during the first growing season had little effect on the production of available twigs for winter moose browse 9 yr after planting. Planted S. alaxensis successfully restored moose habitat at one site, where moose browse production after nine growing seasons was equal to the most productive undisturbed habitat, but browse production was low at the other major planting site. Success was attributed to the similarity of site conditions with sites where vigorous S. alaxensis stands establish naturally, and to the absence of competition from planted revegetation grasses.
TL;DR: Liriomyza trifolii (Burgess) larva populations increased slowly in bell pepper Capsicum annuum L., with some change in stability of age distribution as growing seasons progressed.
Abstract: Liriomyza trifolii (Burgess) larva populations increased slowly in bell pepper Capsicum annuum L., with some change in stability of age distribution as growing seasons progressed. Greatest numbers of leafminer larvae per plant occurred during the reproductive period of plant growth. Damage to plant foliage due to larval feeding fluctuated throughout each season. Total number of mines per plant did not appear to be a good indicator of amount of damage inflicted. Damage appeared to depend on time of season and amount of leaf surface area available.
TL;DR: Seasonal changes in nutrient standing stocks in the vegetation of the mire-grasslands are in the upper part of the range reported for sub-Arctic and Arctic graminoid communities, and low Ca concentrations occur in the plants so that Ca standing stocks are lower than in most comparable northern hemisphere communities.
Abstract: Investigations of the seasonal changes in vegetation standing crop have enabled an assessment of annual net primary production (ANP) at a fjaeldmark, open fernbrake and closed fernbrake at Marion Island (46°54′S, 37°45′E). These communities represent a successional sequence on relatively dry ridges and slopes on the island. Together, they are representative of a large proportion of the island's lowland (c. 300 m above sea level) vegetation. Aboveground ANP's were 728 g m-2 y-1 at closed fernbrake, 502 g m-2 y-1 at open fernbrake and 226 g m-2 y-1 at fjaeldmark. Total (above-plus below) ANP's were 1958 g m-2 y-1, 1578 g m-2 y-1 and 685 g m-2 y-1, respectively. These values are greater than those found for most tundra and tundra-like shrub and dwarf shrub-dominated communities of the northern hemisphere. The island's oceanic climate ensures a long growing season (c. 300 days for vascular plants, 365 days for bryophytes) and aboveground productivities for the island communities (including two mire-grasslands reported on previously), based on the length of the growing season, were 0.9 to 2.9 g m-2 d-1, lower than for most comparable shrub and dwarf shrub sub-Arctic or alpine communities and more similar to low Artic and low alpine sedge-moss and grass-herb communities. Production efficiencies (0.7% to 2.1% of photosynthetically active radiation) were in the range reported for northern hemisphere subpolar vegetations.
TL;DR: These experiments generally support inoculation experiments indicating that G. macrocarpum causes tobacco stunt disease, and fumigation of soil with 67% methyl bromide-33% chloropicrin (MBC) was more effective in increasing growth and accelerating maturity of tobacco in three fields in Central Kentucky infested with the tobacco stunt pathogen.
Abstract: Fumigation of soil with 67% methyl bromide-33% chloropicrin (MBC) was more effective than fumigation with 98% methyl bromide-2% chloropicrin (MB) in increasing growth and accelerating maturity of tobacco in three fields in Central Kentucky infested with the tobacco stunt pathogen. However, both fumigants had similar effects on yields. Two fields had more species of endogonaceous fungi and higher populations of endogonaceous spores than the third, in which the disease was more severe. In all three fields, Glomus macrocarpum was prevalent, reproduced on tobacco, and was controlled by fumigation. For plants growing in nonfumigated soil, height at harvest time was correlated negatively with populations of spores of G. macrocarpum , and less strongly with G. microcarpum and Acaulospora scrobiculata . No such correlations occurred with plants growing in fumigated soil. Roots of plants growing in both fumigated and nonfumigated soil were colonized by mycorrhizal fungi throughout the growing season, but by harvest time, roots of plants growing in nonfumigated soil were colonized 10-fold more than those of plants growing in fumigated soil. However, stunting was not correlated with colonization. These experiments generally support inoculation experiments indicating that G. macrocarpum causes tobacco stunt disease.
TL;DR: The results suggest that the annual shoots of pine are sensitive to frost at the end of their height growth period and that low temperatures during the growing season may be part of the cause of multiple leaders.
TL;DR: Results of this study strongly implicate periodic heavy graxing durhtg the growing season as a primary cause of restricted basal-area growth and lack of reproduction.
Abstract: This study cvahtated the effects of heavy forage use in a restrotation grazing system on the basal-area growth and frequency of occurrence of native bunchgrasses from 1975 to 1984. None of these grasses increased in basal-area cover with brush competition or in basal-area cover or frequency without brush competition when subjected to periodic heavy graxing (65% utihxation in June and 75% in July) during the growing season. When plants were protected from graxing, average basal-area cover increased for Idaho fescue [Fetiucu &fuhoeusii Elmer] and squirreltail/‘Sitani hystrix (NM.) J.G. Sm.] in a Wyoming big sagebrush [Artemi& tridentata wyomingends Beetle+Idaho fescue community type and for Thurber needlegrass [St@ thur* Piper] in 8 Wyoming big sagebrush-bluebunch wheatgrass [Agmpymn spicatutn (Push) Scribn. & Smith] community type. Average basal-area cover was unchanged for protected Thurber needlegrass plants in a Wyoming big sagebrush-Thurber needlegrass community type. Average basal-area cover of Thurber needlegrass plants in the same community type decreased when heavily grazed during the growing season in 1 yeu during the first 3 years of the study and with no grazing during the growing season in the last 4 yeus of the study. Bluebunch wheatgrass showed no differential response to grazing or protection. Results of this study strongly implicate periodic heavy graxing durhtg the growing season as a primary cause of restricted basal-area growth and lack of reproduction. These results support the contention that such grazing pressure can prevent range improvement in an otherwise appropriate rotation grazing system.